How do ask a girl to be my gf (girl friend)?

im 13 and theres this girl i like and shes very pretty and im umm average i think but im really funny,we also have a lot in common , so i have good friends and normal friends and one of my good friends is her friend but im to scared or how ever you spell that i don't know. what would i do just walk up to her and ask her out or have my friends do it idk even know what we do after that hold hands and talk get to know each other and im not the kind of person that walks up 2 girls and ask them out last time i did was in the 6th grade now im in 8th and the ownly reason i know her cuz she did school b-ball and my sister was the coach (and my sis is a cool person )shes also doing track with me and i think she likes me cuz she looks at me some times and have eye contact, and she laughs at my jokes so could any body who isn't an half *** answer me plz cuz creepy enough somtimes i don't sleep 4 this reason, and 1 last thing she has a boy friend but she dumped him for some other 4 another guy and he is an asshole so idk just plz